JP5627520B2 - Image forming apparatus and toner density control method - Google Patents

Description

  The present invention relates to an image forming apparatus and a toner density control method.

  In an electrophotographic image forming apparatus such as a multifunction machine or printer, an electrostatic latent image is formed on a photosensitive drum by an exposure device, and toner supplied from a toner container to a developing device is exposed to a developing roller or a developing sleeve. The toner is developed on the body drum.

  In such an image forming apparatus, a sensor is provided in the developing device so that the toner in the developing device does not run out. When a decrease in the toner amount in the developing device is detected by the sensor, the toner is transferred from the toner container to the developing device. Is supplied. As a result, a sufficient amount of toner is continuously held in the developing unit, the toner supply from the developing unit to the photosensitive drum becomes constant, and fluctuations in toner image density are reduced.

  On the other hand, a certain image forming apparatus is provided with a density sensor that detects a developer density in a developing device, a developer density on a developing roller, a toner image density on a transfer belt to which a toner image is transferred from a photosensitive drum, and the like. In accordance with the output of the density sensor, the toner image density is controlled by controlling the output of the exposure apparatus, the developing bias, and the like (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 2002-62696

  However, if the concentration sensor is provided as described above, the manufacturing cost of the device increases. In particular, it is not preferable that the manufacturing cost is high for a low-priced device.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a toner density control method that appropriately control toner image density without using a density sensor.

  In order to solve the above problems, the present invention is configured as follows.

An image forming apparatus according to the present invention stores a calibration data indicating a correspondence relationship between a plurality of image density setting values and a dot count value at a predetermined toner consumption amount, and toner is determined based on the calibration data. Image density that derives the estimated value of toner image density from the dot count value counted during the period when the toner consumption amount is consumed, and updates the development bias setting value according to the difference between the image density setting value and the estimated value An estimation unit and a calibration data update unit that updates calibration data based on the estimated value described above are provided.

As a result, the toner image density is estimated from the dot count value during that period when the toner is consumed by a predetermined amount of toner using calibration data obtained in advance by experiment or the like, so that the toner can be used without using the density sensor. image density Ru is properly controlled.

Further, even when the calibration data in the initial state is not appropriate due to the tendency of the document to be printed by the user or the change with time of the apparatus, the calibration data is automatically corrected to the calibration data appropriate for the user.

The image forming apparatus according to the present invention, in addition to the image forming equipment described above may be as follows. In this case, the calibration data updating unit, if the difference between the estimated value and the picture image density setting value is greater than the variation limit, and updates the calibration data according to the difference between the estimated value and images concentration setting.

The image forming apparatus according to the present invention may be configured as follows in addition to any of the image forming apparatuses described above. In this case, the calibration data updating unit, larger than the difference variation upper limit value of the estimated value and the picture image density set value, the image density setting value or dot count in the calibration data in accordance with the difference between the difference between the variation upper limit value Shift the value.

The image forming apparatus according to the present invention may be configured as follows in addition to any of the image forming apparatuses described above. In this case, the calibration data updating unit, if the difference between the estimated value and the picture image density setting value is smaller than the variation lower limit value, and updates the calibration data according to the difference between the estimated value and images concentration setting.

The image forming apparatus according to the present invention may be configured as follows in addition to any of the image forming apparatuses described above. In this case, the calibration data updating section, smaller than the difference variation lower limit value of the estimated value and the picture image density set value, the image density setting value or dot count in the calibration data in accordance with the difference between the difference between the variation lower limit value Shift the value.

The image forming apparatus according to the present invention may be configured as follows in addition to any of the image forming apparatuses described above. In this case, the image density estimation unit derives the estimated value without using a density sensor that measures the toner image density.

The toner density control method according to the present invention is based on calibration data indicating a correspondence relationship between a plurality of image density setting values and a dot count value at a predetermined toner consumption amount in a period in which the toner is consumed by the predetermined toner consumption amount. A step of deriving an estimated value of toner image density from the counted dot count value, an image density setting value is determined and updated based on the derived estimated value, and according to a difference between the image density setting value and the estimated value Updating the setting value of the developing bias, and updating the calibration data based on the estimated value.

As a result, the toner image density is estimated from the dot count value during that period when the toner is consumed by a predetermined amount of toner using calibration data obtained in advance by experiment or the like, so that the toner can be used without using the density sensor. image density Ru is properly controlled.

  According to the present invention, the toner image density is appropriately controlled without using a density sensor.

FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a side view showing the developing unit in FIG. 1, and the photosensitive drum and toner container around the developing unit. FIG. 3 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a diagram showing an example of the calibration data shown in FIG. FIG. 5 is a flowchart illustrating toner image density control by the image forming apparatus according to the embodiment of the present invention. 6 is a diagram showing an example of calibration data updated from the calibration data shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. This image forming apparatus is an apparatus having an electrophotographic printing function, such as a printer, a facsimile machine, a copying machine, or a multifunction machine.

  The image forming apparatus of this embodiment has a tandem color developing device. The color developing device includes photosensitive drums 1a to 1d, exposure devices 2a to 2d, and developing devices 3a to 3d. The photoconductor drums 1a to 1d are four-color photoconductors of cyan, magenta, yellow, and black. The photosensitive drums 1a to 1d are made of amorphous silicon, for example.

  The exposure devices 2a to 2d are devices that form electrostatic latent images by irradiating the photosensitive drums 1a to 1d with laser light while scanning. The laser beam is scanned in a direction (main scanning direction) perpendicular to the rotation direction (sub-scanning direction) of the photosensitive drums 1a to 1d. The exposure apparatuses 2a to 2d have a laser scanning unit including a laser diode that is a light source of laser light and an optical element (lens, mirror, polygon mirror, etc.) that guides the laser light to the photosensitive drums 1a to 1d.

  Further, around the photosensitive drums 1a to 1d, a charger such as a scorotron, a cleaning device, a static eliminator and the like are arranged. The cleaning device removes residual toner on the photosensitive drums 1a to 1d after the primary transfer, and the static eliminator neutralizes the photosensitive drums 1a to 1d after the primary transfer.

  The developing units 3a to 3d are connected to toner containers filled with toners of four colors of cyan, magenta, yellow and black, respectively, and supply toner supplied from the toner containers to the photosensitive drums 1a to 1d. A toner image is formed by attaching toner to the electrostatic latent images on the photosensitive drums 1a to 1d.

  The photosensitive drum 1a, the exposure device 2a, and the developing unit 3a develop magenta, and the photosensitive drum 1b, the exposure device 2b, and the developing unit 3b develop cyan, the photosensitive drum 1c, and the exposure device 2c. The developing unit 3c performs yellow development, and the photosensitive drum 1d, the exposure device 2d, and the developing unit 3d perform black development.

  FIG. 2 is a side view showing the developing device 3a and the photosensitive drum 1a and the toner container 11a around the developing device 3a in FIG. Although FIG. 2 shows the periphery of the developing device 3a, the periphery of the developing devices 3b to 3d has the same configuration.

  For example, when the developing device 3a is a two-component developing device, as shown in FIG. 2, the developing device 3a includes a developing sleeve 21 and a magnetic permeability sensor 22 for measuring the amount of toner in the developing device 3a. Have. The toner container 11a is connected to the developing device 3a, and when the toner supply roller 31 of the toner container 11a rotates by a predetermined amount, a predetermined amount of toner is supplied from the toner container 11a to the developing device 3a. When a decrease in the toner amount is detected by the magnetic permeability sensor 22, the toner supply roller 31 is driven by a toner supply motor (not shown), and toner is supplied to the developing device 3a.

  The intermediate transfer belt 4 is an annular image carrier (intermediate transfer member) that comes into contact with the photosensitive drums 1a to 1d and primarily transfers the toner images on the photosensitive drums 1a to 1d. The intermediate transfer belt 4 is stretched around a driving roller 5 and circulates in the direction from the contact position with the photosensitive drum 1d to the contact position with the photosensitive drum 1a by the driving force from the driving roller 5. .

  The transfer roller 6 brings the conveyed paper into contact with the intermediate transfer belt 4 and secondarily transfers the toner image on the intermediate transfer belt 4 to the paper. The sheet on which the toner image has been transferred is conveyed to the fixing device 9 and the toner image is fixed on the sheet.

  The roller 7 has a cleaning brush, and the cleaning brush is brought into contact with the intermediate transfer belt 4 to remove the toner remaining on the intermediate transfer belt 4 after the transfer of the toner image onto the paper.

  FIG. 3 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. As illustrated in FIG. 2, the image forming apparatus includes a printing device 41, an image reading device 42, an operation panel 43, a communication device 44, a storage device 45, and an arithmetic processing device 46.

  The printing apparatus 41 is an internal device that prints a document image on paper with a mechanical configuration as shown in FIG.

  The image reading device 42 is an internal device that feeds a document with, for example, an auto document feeder, optically reads an image of the document page by page, and generates image data of each page image.

  The operation panel 43 is arranged on the surface of the casing of the image forming apparatus, and includes a display device that displays various types of information to the user and an input device that detects a user operation. For example, a liquid crystal display is used as the display device. A key switch, a touch panel, or the like is used as the input device.

  The communication device 44 can be connected to a host device via a network or a peripheral device interface, and performs data communication using a predetermined communication protocol.

  The storage device 45 is a device capable of storing various data and programs. As the storage device 45, a nonvolatile large-capacity storage medium such as a nonvolatile memory or a hard disk drive is used. Calibration data 51 is stored in the storage device 45.

  The calibration data 51 is data indicating a correspondence relationship between a plurality of image density setting values and a dot count value at a predetermined toner consumption amount. In this embodiment, the calibration data 51 includes a plurality of image density setting values (ID setting values, ID: Image Density) and a dot count value at a predetermined toner consumption amount for each toner color to be used. Data indicating the corresponding relationship.

  FIG. 4 is a diagram showing an example of the calibration data 51 shown in FIG. The calibration data 51 shown in FIG. 4 includes five image density setting values at intervals of 0.1 from 1.1 to 1.5, and each image density setting value when 250 mg of toner is consumed by a predetermined toner consumption amount. Dot count value. Further, the calibration data 51 includes information (30 seconds in FIG. 4) of toner supply time (that is, operation time of the above-described toner supply motor) corresponding to the consumption of the predetermined toner consumption of 250 milligrams.

  The calibration data 51 is obtained in advance by, for example, an experiment using an ISO / IEC19752 standard manuscript with an apparatus having an electrophotographic process similar to that of the image forming apparatus.

  The arithmetic processing unit 46 is a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. Various processing units are realized by executing the program by the CPU.

After the image forming apparatus is activated, various programs are appropriately executed by the arithmetic processing unit 46. In this embodiment, a processing unit such as an operating system (not shown), a request processing unit 61, an image processing unit 62, controllers 63 and 64, an image density estimation unit 65, a calibration data update unit 66 is realized by the arithmetic processing unit 46. Is done.

  The request processing unit 61 receives a job execution request (for example, a copy job execution request) based on a user operation on the operation panel 43 or a job execution request (for example, a print job execution request) supplied from the host device, and receives the job request. Execute the job according to. For example, when document data in a predetermined data format such as PDL (Page Description Language) or PDF (Portable Document Format) is received from the host device as a print job execution request, the request processing unit 61 generates an image from the document data. Generate data. This image data is raster image data. When the original image data of the raster image data is received from the host device, the request processing unit 61 directly uses the original data as image data. The image processing unit 62 performs predetermined image processing such as color conversion, gamma correction, and halftoning on the image data, and print data (for example, print image data binarized for each color). Generate. Then, the request processing unit 61 causes the controller 63 to execute printing based on the print data.

  Also, for example, upon receiving a copy job execution request, the request processing unit 61 causes the controller 64 to execute image scanning, and the image processing unit 62 performs predetermined image processing on the image data obtained by the image scanning. To generate print data. Then, the request processing unit 61 causes the controller 63 to execute printing based on the print data.

  The controller 63 is a processing unit that monitors and controls the printing apparatus 41. The controller 63 controls a toner source development, transfer and fixing by controlling a driving source (not shown) for driving the above-described roller, a bias application circuit for applying a development bias and a primary transfer bias, and exposure apparatuses 2a to 2d. And a processing circuit for executing paper feeding, printing, and paper ejection. The developing bias is applied between the photosensitive drums 1a to 1d and the developing devices 3a to 3d (the developing sleeve 21 in FIG. 2), respectively, and the primary transfer bias is the photosensitive drums 1a to 1d and the intermediate transfer belt 4. Between the two.

Further, the controller 63 determines the developing bias voltage value according to the image density setting value determined by the image density estimating unit 65.

  Further, the controller 63 has a dot counter for counting the number of dots in the print image by the printing apparatus 41 based on the print data, and the dot count value (cumulative value) is calculated every time a print job or one page is printed. Update.

  Further, the controller 63 controls the toner supply motor (not shown) to operate the toner supply roller 31 when the magnetic permeability sensor 22 detects a decrease in the toner amount in the developer 3a. The toner is supplied from the toner container 11a to the developing device 3a. At this time, the controller 63 specifies the operation time (that is, toner supply time) of the toner supply motor in one toner supply, and updates the accumulated value of the toner supply time each time the toner supply roller 31 is operated. This toner supply time corresponds to the toner supply amount (that is, toner consumption amount) from the toner container 11a to the developing device 3a. The controller 63 similarly specifies the toner supply time for the developing devices 3a to 3d, and calculates the accumulated value.

  The controller 64 is a processing unit that monitors and controls the image reading device 42.

The image density estimator 65 does not use a density sensor that measures the toner image density, but based on the calibration data 51, the toner image density is calculated from the dot count value counted during the period in which the toner is consumed by a predetermined toner consumption amount. and out guide the estimates.

The calibration data update unit 66 updates the calibration data 51 based on the estimated value derived by the image density estimation unit 65. In this embodiment, the calibration data update unit 66 updates the calibration data 51 for each toner color to be used.

In this embodiment, the calibration data update unit 66, if the difference between the images concentration setting and the estimated value is greater than the variation limit, the calibration according to the difference between the estimated value and the picture image density setting value data 51 Update. Specifically, the calibration data update unit 66, if the difference between the images concentration setting and the estimated value is greater than the variation limit, the image density in the calibration data 51 in accordance with the difference between the difference between the variation upper limit value Shift the set value or dot count value.

Further, in this embodiment, the calibration data update unit 66, if the difference between the images concentration setting and the estimated value is smaller than the variation lower limit value, in accordance with the difference between the estimated value and images concentration setting Calibration Data 51 is updated. Specifically, the calibration data update unit 66, if the difference between the images concentration setting and the estimated value is smaller than the variation lower limit value, the image density in the calibration data 51 in accordance with the difference between the difference between the variation lower limit value Shift the set value or dot count value.

  Next, the operation of the image forming apparatus will be described.

  FIG. 5 is a flowchart illustrating toner image density control by the image forming apparatus according to the embodiment of the present invention.

When the image forming apparatus is activated, the image density estimation unit 65 monitors whether or not the cumulative value of the toner supply time measured by the controller 63 has reached the toner supply time specified by the calibration data 51 ( Step S1). Note that the cumulative value of toner supply time and the dot count value are stored in the non-volatile storage device 45 and are continuously counted even when the power of the image forming apparatus is turned on / off.

When the cumulative value of the toner supply time measured by the controller 63 has reached the toner supply time specified by the calibration data 51, the image density estimation unit 65 and the calibration data update unit 66 execute the following processing. .

First, the image density estimation unit 65 refers to the calibration data 51 and estimates an actual image density value (hereinafter referred to as an estimated ID value) from the dot count value by the controller 63 at this time (step S2). If the same dot count value as the dot count value by the controller 63 does not exist in the calibration data 51, the estimated ID value is calculated by interpolation or extrapolation.

  For example, when the calibration data 51 is as shown in FIG. 4, if the dot count value is 35 million dots, the estimated ID value is 1.3, and if the dot count value is 42.5 million dots, the estimated ID value is 1 If the dot count value is 50 million dots, the estimated ID value is 1.0.

Then, the image density estimating unit 65 is equal to or less than the difference between the predetermined variation limit of the estimated ID value and the picture image density set value and determines whether a predetermined variation lower limit value or more (Step S3) . Here, the fluctuation upper limit value is a positive value, and the fluctuation lower limit value is a negative value.

If the difference between the images concentration setting and the estimated ID value is a predetermined variation is more than the upper limit and the predetermined variation lower limit value or more, the image density estimating unit 65, variation (images the density of the image concentration value The development bias setting value is updated according to the difference between the setting value and the estimated ID value (step S4).

The correspondence relationship between the change in the image concentration value and the change in the developing bias set value is obtained in advance by experiments or the like, the image density estimating unit 65, based on the correspondence relation, the development of the controller 63 Update the bias setting.

For example, when the change of image concentration value of +0.1, a change in the developing bias set value is +1, when the change of image concentration value is -0.1, the developing bias set value If variation is -1, 10-fold change in image concentration value is a change in the developing bias set value. The actual development bias voltage can be obtained by multiplying the development bias setting value by a predetermined coefficient.

On the other hand, when the difference between the estimated ID value and the picture image density setting value is not less than a predetermined variation limit, the image density estimating unit 65 updates the set value of the developing bias in accordance with the variation upper limit value (step S5) . Further, when the difference between the estimated ID value and the picture image density setting value is not predetermined variation lower limit value or more, the image density estimating unit 65 updates the set value of the developing bias in accordance with the variation lower limit value (step S5) .

Then, when the difference between the estimated ID value and the picture image density setting value is not less than a predetermined variation limit, the calibration data update unit 66 based on the estimated ID value, and updates the calibration data 51 (step S6) . Further, when the difference between the estimated ID value and the picture image density setting value is not predetermined variation lower limit value or more, the calibration data update unit 66 based on the estimated ID value, and updates the calibration data 51 (step S6) .

In this case, the calibration data updating unit 66, if the difference between the images concentration setting and the estimated ID value is greater than the variation limit, the image density setting in the calibration data 51 in accordance with the difference between the difference between the variation upper limit value Shift the value or dot count value. Also, calibration data update unit 66, is smaller than a difference variation lower limit value of the images concentration setting and the estimated ID value, the image density set values in the calibration data 51 in accordance with the difference between the difference between the variation lower limit value Or shift the dot count value.

FIG. 6 is a diagram showing an example of calibration data 51 updated from the calibration data 51 shown in FIG. For example, calibration data 51 before the update is as shown in figure 4, an images density setting value is 1.3, when the change limit value is -0.2, the estimated ID value is 1.0 When, as shown in FIG. 6, the difference between the images concentration setting (1.3) and the estimated ID value (1.0) the difference between (-0.3) and variable lower limit (-0.2) The dot count value corresponding to each ID value in the calibration data 51 is increased by the dot count value (5 million dots) corresponding to (−0.1).

Then, the image density estimation unit 65 sets the development bias setting value obtained in step S4 or step S5 in the controller 63 (step S7), and resets the cumulative toner supply time value and the dot count value in the controller 63 to zero. (Step S8).

As described above, when the cumulative value of the toner supply time measured by the controller 63 reaches the toner supply time specified by the calibration data 51, the image density estimation unit 65 performs the above-described processing, and then the image density estimation unit 65 The process returns to the monitoring (step S1) as to whether or not the cumulative value of the toner supply time measured by (1) has reached the toner supply time specified by the calibration data 51.

As described above, according to the above-described embodiment, the storage device 45 stores the calibration data 51 indicating the correspondence between the plurality of image density setting values and the dot count value at a predetermined toner consumption amount. Then, based on the calibration data 51, the image density estimation unit 65 derives an estimated value of the toner image density from the dot count value counted during a period in which the toner is consumed by the predetermined toner consumption amount, and the calibration data update unit 66 updates the calibration data 51 based on the estimated value described above.

As a result, the toner image density is estimated from the dot count value in the period when the toner is consumed by a predetermined amount of toner using the calibration data 51 obtained in advance by an experiment or the like, without using the density sensor. toner image density Ru is properly controlled.

Further, even when the calibration data in the initial state is not appropriate due to the tendency of the document to be printed by the user or the change with time of the apparatus, the calibration data is automatically corrected to the calibration data appropriate for the user.

  The above-described embodiments are preferred examples of the present invention, but the present invention is not limited to these, and various modifications and changes can be made without departing from the scope of the present invention. is there.

  For example, the image forming apparatus according to the above embodiment is a color electrophotographic image forming apparatus, but may be a monochrome electrophotographic image forming apparatus.

  The present invention is applicable, for example, to toner density control in an image forming apparatus that does not have a density sensor.

45 Storage Device 51 Calibration Data 65 Image Density Estimation Unit 66 Calibration Data Update Unit

Claims (7)

In an image forming apparatus that adjusts a toner image density based on an image density setting value,
A storage device for storing calibration data indicating a correspondence relationship between a plurality of image density setting values and a dot count value at a predetermined toner consumption amount;
Based on the calibration data, an estimated value of toner image density is derived from a dot count value counted during a period in which toner is consumed by the predetermined toner consumption amount, and a difference between the image density setting value and the estimated value is derived. An image density estimation unit that updates the setting value of the development bias according to
A calibration data update unit that updates the calibration data based on the estimated value;
An image forming apparatus comprising:   The calibration data update unit updates the calibration data according to the difference between the image density setting value and the estimated value if the difference between the image density setting value and the estimated value is larger than a variation upper limit value. The image forming apparatus according to claim 1, wherein:   If the difference between the image density setting value and the estimated value is larger than the variation upper limit value, the calibration data update unit determines the image density setting value in the calibration data according to the difference between the difference and the variation upper limit value. The image forming apparatus according to claim 2, wherein the dot count value is shifted.   The calibration data update unit updates the calibration data according to the difference between the image density setting value and the estimated value if the difference between the image density setting value and the estimated value is smaller than a variation lower limit value. The image forming apparatus according to claim 1, wherein:   If the difference between the image density setting value and the estimated value is smaller than the variation lower limit value, the calibration data update unit determines the image density setting value in the calibration data according to the difference between the difference and the variation lower limit value. The image forming apparatus according to claim 4, wherein the dot count value is shifted.   6. The image forming apparatus according to claim 1, wherein the image density estimation unit derives the estimated value without using a density sensor that measures the toner image density. apparatus. In a toner density control method for adjusting a toner image density based on an image density setting value,
Based on the calibration data indicating the correspondence between the plurality of image density setting values and the dot count value at the predetermined toner consumption amount, the toner image is obtained from the dot count value counted in the period in which the toner is consumed by the predetermined toner consumption amount. Deriving an estimated density value and updating a developing bias setting value in accordance with a difference between the image density setting value and the estimated value ;
Updating the calibration data based on the estimated value;
A toner concentration control method comprising:

Images